Modern, computer-assisted surgery is able, with the aid of medical navigation systems, to show the surgeon's instruments or implants in relation to anatomical image data on a monitor during the operation. The anatomical image data of a patient can be acquired either pre-operatively or intra-operatively and can consist of various modalities (CT, MRI, PET, SPECT, x-ray images or combinations of these).
In computer-assisted surgery, it is also common to ascertain image data with the aid of an x-ray device, generally used in the form of a C-arm, and to then utilize this data with the aid of a navigation system. The computer system processes the image data and “registers” it, i.e., the system determines the exact position of image data in relation to a previously defined reference, for example, spatially on the patient. It is then possible to show the position of an instrument on top of the data obtained, i.e., to navigate.
X-ray-based navigation has the advantage that it enables the surgeon, through a very simple registering method, to easily, simply, and quickly enlist the aid of navigation. In isolation, x-ray navigation provides a valuable aid for the surgeon. However in the methods currently used, it has the disadvantage that every image has to be registered individually and then displayed in correct relation to the instruments or apparatus.
Furthermore, systems exist which use navigation based on volume data sets (for example, CT, MRI) and x-ray images and/or reconstructed x-ray images, which are to be registered individually and are reconstructed from the volume data set or from processed x-ray image sets. While these x-ray images, in their original state, actually provide very good imaging data with a high contrast and good accuracy of detail, these advantages are partly lost when the data is converted into a 3D volume data set or is calculated back again to reconstructed x-ray images. In this case, the surgeon then has to navigate using image data which image content is not as good as that of the originally acquired x-ray images.
A surgical navigation system including a reference and localizing frame is known from WO 96/11624. U.S. Pat. No. 5,980,535 discloses a device for an anatomical tracking method in which positional signals are processed, which originate from a reference object on a swing arm of a head clamp.
U.S. Pat. No. 6,314,310 B1 discloses an x-ray-guided surgical localizing system with an extended mapping volume in which x-ray images from a fluoroscope (C-arm) x-ray device are registered in relation to surgical instruments via reference elements. A method and a device for the image-assisted treatment of treatment targets, including the integration of x-ray detection and a navigation system, is known from DE 199 17 867 A1. U.S. Pat. No. 6,048,097 demonstrates an x-ray examining device comprising a C-arm, wherein isocentric irradiation is performed in at least one position of the C-arm.